A (very) Brief History of René Descartes

Please note that in the YouTube description, we have links to Discord, Patreon, and the sources that I referenced to be able to make this video. Rene Descartes was a 17th century philosopher, mathematician, and physicist. He's regarded as both the father of analytic geometry and modern philosophy. Notable contributions include introducing skepticism as a fundamental part of the scientific method, the statement, I think, therefore I am, the Cartesian plane, Descartes' rule of signs, and his own laws of motion. Descartes was born on March 31st, 1596 in La Haye-en-Torraine, in the province of Torraine, which is now Descartes-Entre-Loires. His parents were Joachim Descartes, who studied law and was a counselor in the Parliament of Brittany, which sat in Rennes, and Jeanne Brochardt, the daughter of Rene Brochardt, a man who formed part of the garrison stations at Portier. Before Descartes was born, the pair had two other children, Pierre and Jeanne. Mother Jeanne died in childbirth a year after Descartes was born, and the boy, born at the time of her death, also died. Descartes then went to live with his maternal grandmother, Jeanne Sainte-Brochardt, in La Haye. Joachim remarried in 1600 to a woman named Anne Mulron, having two children, named Joachim and Anne. Descartes never ended up living with a new family, and instead continued to live at his grandmother's home. Easter of 1607, Descartes was enrolled into the Jesuit college, Réal-Henri-le-Grand, at La Flèche in Anjou. Considering Descartes' age at the time of enrollment, this was later than most students. This can be attributed to Descartes' health being rather fragile as a child, probably due to tuberculosis. He was allowed to sleep until 11am because of his health, as opposed to 5am like his peers, and proceeded to hold this sleep schedule the majority of his life. At Legrand, Descartes studied classics, logic, and traditional Aristotelian philosophy. He was also introduced to mathematics and physics, studying primarily arithmetic, algebra, geometry, music, and astronomy, which included work from Galileo. In 1614, Descartes graduated from Legrand, and it had occurred to him upon leaving how little he actually knew. He only found mathematics to be satisfactory, which would become the foundation for his way of thinking. Not much is known about Descartes during the time between 1614 and 1618, other than him attending the University of Poitiers from 1614 to 1616 to get a bachelor's degree in law, per his father's wishes, finding quickly this was not what he wanted to do. It is also known that he lived in Paris for a couple of years, largest keeping to himself, and it is suspected that he was suffering from a mental breakdown during this time. In 1618, Descartes' aim was to become a professional military officer. He enrolled in the military school at Breda and became a volunteer in the Protestant Dutch State's army under Maurice of Nassau, who was the stadholder of all provinces of the Dutch Republic at the time. Descartes' formal study was mechanical engineering, but was able to study both mechanics and mathematics under Isaac Beekman, a 17th-century Dutch philosopher and scientist often credited with giving birth to atomism, the theory that physical universe is made up of atoms. Under Beekman's direction, Descartes started seeking a unified science of nature. In 1619, Descartes began service for Catholic Duke Maximilian of Bavaria, being stationed in Ulm. Under the Bavarian service, while stationed in Neuberg under Dunau, Descartes had three revolutionary dreams, sparking his formulation of analytic geometry, his idea that the pursuit of science would prove to be the pursuit of true wisdom, and his belief that all truths were linked with one another, so that finding a fundamental truth and proceeding with logic would open the way to all of science. In 1620, Descartes left the army and proceeded on a nomadic venture across Europe for the next few years. He was able to fund this after selling property his father gifted him, with such sale allowing him to live without monetary worry for the rest of his life. Descartes spent time in various places which include Bohemia, Hungary, Germany, Holland, and Italy. He made a few rounds to France as he traveled about, making contact with mathematicians such as Mérgine Mersenne, a 17th century French polymath notable for Mersenne prime numbers and his work on music theory, which got him the name the father of acoustics, Claude Maidorge, a 17th century French mathematician notable for his work on optics and conic sections, and Girard du Sarg, a 17th century French mathematician notable for being the founder of projective geometry. In 1625, Descartes decided to settle in Paris, and his home over the next few years would become more and more of a hot spot for philosophers and mathematicians to hang out. By 1628, Descartes grew tired of this lifestyle, as well as how nomadic he'd been, and wished for a more peaceful existence. He decided Holland would be perfect for him, and other than really Mersenne, Descartes kept his residence private. In 1629, Descartes enrolled and studied at the University of Franeker, studying under mathematician and astronomer Adriaen Medius, notable for his work in geometry and manufacturing astronomical instruments. In 1630, Descartes enrolled and studied at Leiden University, where he studied mathematics and physics under the direction of Jacob Golias, a 16th century Dutch orientalist and mathematician, mostly known for being an orientalist, publishing many Arabic to Latin translations, and Martin Hortensius, a 16th century astronomer and mathematician, notable for developing a method for measuring the diameters of planets based on the measured visual angle that his telescope revealed. In October of 1630, after years of correspondence, Descartes had a falling out with Baikman over claims of plagiarism. Throughout his career, Descartes had a tendency to never credit others, claiming all of his ideas to be original, which was often not the case. In 1633, Descartes had intentions of publishing a work entitled Le Monde. The work defended the heliocentric view of the universe, Galileo's view, which challenged the geocentric view the Catholic Church held. With Galileo being put on trial and then being condemned to house arrest, Descartes did not want to suffer the same fate and decided against publishing the work. He was urged by the likes of Madoge and Mersenne to publish the work, but Descartes was adamant about not doing so, and the work as a whole wasn't published until 1664, quite a few years after Descartes' death. Although Descartes was never put on trial, he definitely got himself in hot water with the Church and those affiliated. His published philosophy, which went on to be highly influential, changed the line of questioning from what is true to of what can I be certain, shifting the guarantor of truth from God to humanity. Such reasoning led his work to be banned at various institutions during his lifetime, such as the University of Utrecht in 1643, as well as his work being placed in the Catholic Church's Index of Prohibited Books in 1663, which was discontinued in 1966, and his work being banned under Louis XIV's reign in 1671. In 1635, Descartes had a love child with his housekeeper, Helena Jansvanderstrom. Their daughter was named Francine, and they lived part-time with Descartes, and since Helena and Descartes were unmarried, Descartes told people Francine was his niece. The intention was for all of them to live together as a family, full-time, but Francine died of scarlet fever before this could happen in 1640. Helena eventually married someone in 1644, and Descartes paid for the wedding dowry. In 1637, still not wanting to publish Le Monde, Descartes decided to publish certain parts of the work as appendices to Discourse on the Method, which was an attempt to explain his method of reasoning, with some of the main ideas being, be a skeptic, doubt until there is a sufficient amount of evidence to wash the doubt away, break problems down into the smallest amount of parts necessary to provide an adequate solution, and order your thoughts from simplest to hardest, ascending little by little through the chain. This work also introduced Descartes' most famous quote, I think, therefore I am. The appendices to Discourse were Les Métiers, La Diertrique, and La Diamanterie. Les Métiers was a work on meteorology, important in being the first work to attempt putting the study of weather on a scientific basis. Most of the claims Descartes made in this work are wrong, and could have easily been shown to be wrong had Descartes performed some simple experiments. One example is the commonly held belief of the time that water which had been boiled froze more easily. La Diertrique was a work on optics, largely notable because of Descartes' approach to experiment. It didn't introduce many new ideas, and didn't credit previous scientists' work accordingly, with an example being the derivation of the law of refraction. The primarily 16th century mathematician and physicist Willard Broad Snell was most notable for being the first to mathematically formulate the law in 1621, though he never formally published the result. It's suspected that Descartes had repeated Snell's experiments around 1626, forgetting how much he owed to Snell's work. La Diamanterie is arguably Descartes' most important contribution, tying together algebra and geometry, and had immense influence on Sir Isaac Newton and Gottfried Wilhelm Leibniz in developing their independent forms of calculus. It must be noted that Descartes' exposition initially limited the circulation and appreciation of the work, and it wasn't until later translations, the first being in 1649, that the work became widely read. There were many notable results in the work, which included a method for finding tangent lines to curves, the introduction of Descartes' rule of sines for determining the number of positive real roots of a polynomial, the introduction of the superscript notation for exponents, as well as using ABC and XYZ for knowns and unknowns, respectively, showing one could solve equations of degree greater than three, which previously made no sense to people since, geometrically, we can only perceive up to three dimensions, and introducing the world to the Cartesian plane, though this plane was only introduced properly in future editions of this work, notably a Latin translation from Franz von Schutten in 1659. Similar work had been done independently by Pierre de Fermat in a work entitled Introduction to Plane and Solid Loci, which actually showed a similar method for finding tangent lines to curves. This work began circulating around in 1636, a year before La Géométrie was published, and this enraged Descartes, as he felt it undermined his own work, and essentially tried to ruin Fermat's mathematical career, with great success, mind you, as Introduction to Plane and Solid Loci wasn't officially published until 1679, well after Fermat's death. In 1641, Descartes published Meditations on First Philosophy, and it is his most famous philosophical work. It's a work on metaphysics, exploring ideas such as the existence of God, constructing an ontological proof, mind-body dualism, which is the theory that the mind and body are distinct and separable, that humans are simply a union of the two, and the concept of modes, which are ways in which substances exist. Due to the subject matter, many scientists at the time were opposed to the ideas expressed in the work. In 1644, Descartes published Principles of Philosophy, his most comprehensive philosophical work, where he dug much deeper into the concepts he explored in Meditations on First Philosophy, as well as attempting to put the whole universe on a mathematical foundation. He reduced the study to that of mechanics, introducing his own laws of motion that would go on to have influence on Newton's work. The first two laws basically roll up into Newton's Law of Inertia, and his third law states that a body, upon coming in contact with a stronger one, loses none of its motion, but upon coming in contact with a weaker one, loses as much as it transfers to that weaker body. He also introduced his now-disproven vortex theory, which is the hypothesis that colliding particles supply the force that pushed planets toward the sun. Despite vortex theory being wrong, it was very important in pushing physics in the right direction. In 1647, a French translation of Principia was made by a man named Abbot Claude Picot, and it was dedicated to Princess Elizabeth of Bohemia, who had correspondence with Descartes for a total of six years, primarily discussing issues around morality and psychology. In 1649, Descartes published The Passions of the Soul, which was greatly influenced by the correspondence with Princess Elizabeth, and was also dedicated to the princess. The work discussed the belief of the time that the human body contained animal spirits, which ultimately affected the human soul, or passions of the soul, distinguishing six basic passions—wonder, love, hatred, desire, joy, and sadness. Descartes argued these passions influenced the soul to will or want certain actions, and he also argued that fear is a passion that moves the soul to generate a response in the body. By 1649, Descartes was acclaimed across Europe as a tutorer on his ideas about love, as she rather enjoyed the philosophies than the passions of the soul. Descartes accepted, and moved to Sweden midwinter, and this decision would prove to be problematic. Moving to tutor the queen required Descartes to break his 11am wake-up schedule, and wake up at 5am three days a week to tutor her. Over a few months, the pair found they weren't very fond of each other, and Descartes' health was plummeting due to his new wake-up schedule mixed in with the poor insulation of the castle. On February 1st, 1650, Descartes contracted pneumonia, and on February 11th, died from it. He was first buried in a graveyard for orphans, in Adolf Friedrichskirche in Stockholm. In 1666, his remains were taken to France, and he was buried in Saint-Étienne-du-Monde. And in 1819, he was reburied in the Abbey of Saint-Germain-des-Presse. Well, there you have it. A brief history on another brilliant mind. We'll end on a quote from Descartes' work, The Principles of Philosophy. When we make use of false principles, we depart the farther from the knowledge of truth and wisdom exactly in proportion to the care with which we cultivate them, and apply ourselves to the deduction of diverse consequences from them, thinking that we are philosophizing well, while we are only departing the farther from the truth, from which it must be inferred that they who have learned the least of all that has been hitherto distinguished by the name of philosophy are the most fitted for the apprehension of truth. If you enjoyed the video, please click that like button and subscribe. And if you generally just enjoy the content of this channel, please consider supporting on Patreon. As always, thank you for watching, and I'll catch you next time.